Surface improvement for erosion resistance

ABSTRACT

The technique of laser induced surface improvement is used for tool surfaces in downhole tools that experience erosion from slurry or high velocity flows.

FIELD OF THE INVENTION

The field of this invention is surface improvements of parts of downholetools that are subject to wear and erosion from fluid flow, includingheavily laden fluids such as slurry, and more particularly to surfaceimprovements applied with lasers.

BACKGROUND OF THE INVENTION

There are many downhole operations that involve slurry flow or highvelocity gas flow with entrained solids. Such flows tend to remove metalfrom parts and can cause them to fail to operate or, in extreme cases,sever parts that may need to be fished or milled out. One commonprocedure is gravel packing through a crossover. This entails pumpinggravel slurry past several bends to get it out from tubing and into theannular space defined by a surrounding casing. The crossover passagescan exhibit high wear from the gravel impacts at relatively highvelocities. Downhole choke valves generally have a ported cage moving toalign the port thereon with an opening in the choke housing. The onsetof flow as such valves open brings a rush of high velocity gas throughan initially small opening. Here again, this mode of operation can causesevere wear from the erosion of the high velocity gasses.

In the past, the wear resistant surfaces were made from hard materialsthat resisted the erosive effects of the slurry flow. In someapplications the wear surfaces were applied over a support surface andupon sufficient wear the remainder of the surface could be removed andreplaced. These sacrificial liners were expensive to apply and replaceand the present invention addresses the problem of economicallyincreasing the life of components subjected to erosive forces due toslurry flows or high velocity gas flows downhole.

A technique called Laser Induced Surface Improvement (LISI) has beenused to clad a surface with a metal coating and a binder that arealloyed to the surface using a laser. These techniques have beendeveloped at the University of Tennessee with cooperation from theGeneral Motors Corporation and have resulted in patents principallytargeted to the automotive industry. The present invention seeks toapply this technique to downhole applications where erosion is a problemas an improvement to the existing technology of putting a hard surfacein the wear zones.

Some patents that illustrate the LISI technique are U.S. Pat. Nos.5,503,703; 5,961,861; 5,985,056; 6,016,227; 6,173,886; 6,223,137;6,229,111; 6,284,067; 6,294,225; 6,299,707; 6,328,026; 6,350,326;6,423,162; 6,497,985 and 6,660,692. These patents are all incorporatedby reference as if fully set forth.

SUMMARY OF THE INVENTION

The technique of laser induced surface improvement is used for toolsurfaces in downhole tools that experience erosion from slurry or highvelocity flows.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a multi-port sub with the coating placed on it usingthe LISI technique.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a circulation sub 10 that has a central passage 12and one or more lateral outlets 14. Using the LISI process, a coating 16is adhered to the surfaces that define the outlet 14. Optionally, thewall of passage 12 can also be coated.

While a circulation sub is illustrated those skilled in the art willrealize that other downhole tools that experience slurry flow thatcreates an erosion issue or high, velocity fluids can benefit from thewear coating adhered with the LISI process. The thickness and materialselection can vary with the anticipated severity of the service andcompatibility with fluids downhole.

Another downhole application is cross-over subs where gravel slurry goesfrom the tubing into the surrounding annulus. That flow can damage theports or the opposing casing or control lines in the wall of the tool.Other applications involve sliding sleeves, frac nipples, seal boresurfaces, chokes and washout tools, to illustrate a few examples.

The LISI process improves surface properties such as hardness, wearresistance or corrosion resistance. In use the technique calls forapplication of a coating layer that is melted to the substrate so thatthe chemical composition or/and the microstructure of the substrate arealtered. The underlying surface is preferably sand blasted, washed andthen dried. A precursor which is a suspension of powder materials in awater soluble binder is prepared and sprayed on the surfaces to betreated in a thickness of about 50-150 μm and preferably less than 200μm and then dried. The laser is then applied to unite the coating andthe substrate. The surfaces coated can be flat, inner diameters or outerdiameters, for example. The new surface after laser application can besand blasted or left in its original state. Optionally, it can betextured on a steel substrate.

Some of the advantages of the LISI process are control of thickness anddilution of the layer secured by the process, an ability to focus onspecifically targeted surfaces, the creation of a property modificationof the surface, an environmentally friendly process with efficientmaterial use, a broad range of substrates and reinforcement materialsthat can be integrated with them, rather small heat affected zones(under 10 microns) and a metallurgical bond so that the risk ofdelaminating is not present.

As a result of the LISI process the affected surface is hard, thick anddense while being metallurgically bonded while minimally damaging theunderlying material. The process is flexible allowing for targeting ofspecific surfaces and options on coating selection such as WC, ZrO₂, TiNor CrB₂. There are a number of other material options including, but notlimited to these carbides, ceramics, and oxides: CrB₂, Cr₃C₂, TiB2,Nb₂C, TiC, B₄C, SiC, Mo₂C, SiC, ZrB₂, WC, WZrC, MoB, TiB₂ or CrB₂. Aftertreatment with the LISI process, downhole tools can permit higher flowrates of streams that previously caused erosion such as gravel slurriesor high velocity fluid flows.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below.

1. A tool for use in erosive service downhole comprising a surface incontact with an erosive stream that is made more durable by anapplication of a precursor laser melted onto the surface.
 2. The tool ofclaim 1, wherein said surface comprises a part of a cross-over tool, achoke, a frac nipple, a seal bore, a washout tool, or other down-holeorifice where fluid flow erodes the orifice.
 3. The tool of claim 1,wherein said precursor comprises at least one of oxides, ceramics,nanoparticles, nitrides, silicides, and metals, such as: CrB₂, Cr₃C₂,TiB2, Nb₂C, TiC, B₄C, SiC, Mo₂C, SiC, ZrB₂, WC, WZrC, MoB, TiB₂ or CrB₂.